Writing instrument



FIG. 1 is bottom view of an ornamental design for a writing instrumentdesign according to the present invention;

FIG. 2 is a first front view thereof in the extended configuration;

FIG. 3 is a second front view thereof in the extended configuration;

FIG. 4 is a third front view thereof in the retracted configuration;

FIG. 5 is a left side view thereof in the retracted configuration;

FIG. 6 is a perspective view thereof; and,

FIG. 7 is a back view thereof in the retracted configuration.

CLAIM The ornamental design for a writing instrument, as shown anddescribed.